Portable rubbing machine



April 2 1953 H. R. JOHNSON 2,635,396

PORTABLE RUBBING MACHINE Filed June 2, 1949 4 Sheets-Sheet l April 21,1953 H. R. JOHNSON PORTABLE RUBBING MACHINE 4 Sheets-Sheet 2 Filed June2,' 1949 www www uw mwN @N QW/df j? NNN Apri! 2L 1953 H. R. JOHNSON2,635,396

PORTABLE RUBBING MACHINE Filed June 2, 1949 4 sheets-sheet 5 PI 21, 1953H. R. JOHNSON 2,635,396

PORTABLE RUBBING MACHINE Filed June 2, y 1949 4 Sheets-Sheet 4 86 ZZ .7l ./@3 Q7 Z9 @5 f77 175 ll JZ@ J70 Y 69 .1 -v i 1741 @a i. 12637 f 1 ls" /13 z? jge| l gz 73 l /1/2 70 L 1 72? mi 175 53 'w l 167//////,//7,W//,/ d l" I *l a 156 a 7 172 Z? j! rif. I i

154/ fw' i fa Patented Apr. 21, 1953 PORTABLE RUBBING MACHINE Harold R.Johnson, Rockford, Ill., assignor, by

mesne assignments, to The Porter-Cable Machine Company, Syracuse, N. Y.,a corporation of New York Application June 2, 1949, Serial No. 96,671

1 Claim. 1

l This invention relates to portable rubbing machines, and moreparticularly to such machines which are operated by fluid under pressureand adapted to manual manipulation for sanding, polishing and the like.

One of the objects of my invention is to provide a portable uid operatedrubbing machine wherein the actuating parts are built into the body ofthe machine, and wherein tubes are cast into the body to provide fluidpassages, thereby avoiding the necessity of a sizable number ofrelatively diicult and costly drilling operations.

As another object, my invention has within its purview the provision ofa fluid operated rubbing machine having an actuating mechanism builtinto the body of the machine and so constructed and arranged that themachine body serves as an exhaust muilier.

My invention has for another object the provision of a piston actuated,uid operated rubbing machine in which the piston movements and energyare transferred directly to the rubbing surface.

It is a further object of the invention to provide a fluid operatedrubbing machine embodying a valve having relatively few parts of ruggedconstruction and which is mounted for ready and convenient access.

I have further provided, in the disclosed rubbing machine, a manuallyoperable actuating element for controlling the operation f the machine,which actuating element is normally biased to a position such that themachine is shut off, and which is disposed and contoured relative to theportion of the machine normally gripped in use so that normal grippingpressures effect control of the machine operation with negligibleconscious effort and no appreciable discomfort.

The structure of my rubbing machine adapts it to both wet and dryrubbing operations and is such that the liquid for wet rubbingoperations is fed through the body of the machine and discharged at aneiective position relative to the rubbing surfaces by an attached jet,and in addition to which, the flow of liquid, as well as the operationof the machine may be controlled by a control member on the machinebody.

It is further within the purview of this invention to provide relativelyinexpensive, but effective and quickly operable clips for holdingrubbing surface material in place on the rubbing shoes of my rubbingmachine.

Other objects and advantages of the invention will be apparent from thefollowing description and the accompanying drawings in which similarcharacters of reference indicate similar parts throughout the severalviews.

Referring to the four sheets of drawings,

Fig. 1 is a perspective view taken from one end and to one side of aportable rubbing machine embodying a preferred form of this invention;

Figs. 2 and 3 are fragmentary end elevational views of a portion of thestructure illustrated in Fig. 1 and wherein dierent positions of movableparts are illustrated;

Fig. 4 is a top plan view of the structure shown in Fig. 2;

Fig. 5 is a general and substantially central side sectional view of theportable rubbing machine illustrated in Fig. 1;

Fig. 6 is a fragmentary end View with a portion cut away and takensubstantially at the position indicated by a line 6--6 in Fig. 5 whenviewed as indicated by accompanying arrows;

Fig. 7 is a fragmentary side elevational view of a portion of thestructure shown in Fig. 5 and wherein a part is cut away to illustratecertain details of internal structure;

Fig. 8 is an end elevational view taken substantially as indicated by aline 8 8 in Fig. '7 and accompanying arrows;

Fig. 9 is a sectional view taken substantially on a line 9 9 of Fig. 5and viewed in the direction indicated by the arrows;

Fig. 10 is a sectional view taken substantially on a line l0-l0 of Fig.5 and in the direction indicated by arrows;

Fig. 11 is a fragmentary, perspective, exploded view depicting certainpreferred forms of parts and indicating their preferred order andarrangement in assembly for use in my portable rubbing machine;

Fig. 12 is a bottom plan View taken substantially at the positionindicated by a line I2-I2 in Fig. 5 and in the direction of theaccompany'- ing arrows; and

Figs. 13 and 14 are fragmentary top sectional views depicting differentoperating positions of parts of the structure which are illustrated inFig. 11.

In general, the exemplary embodiment of my portable rubbing machine,which is shown in the accompanying drawings for illustrative purposes,includes a body 20 exteriorly contoured with smooth and rounded curvesand with side indentations such as 22, so that the body, in addition toother purposes, serves as a hand grip by which the machine ismanipulated in use.

At one end of the top of the body, an actuator 23 is movably mounted inrecess 24 for controlling the operation of the machine. By preference,this actuator is nearly flush with the adjoining surfaces of the bodyand conforms generally to the body contours, so that it is not onlyaccessible for operation by a convenient gripping action, but also sothat its projection beyond the body surface is insuicient to causedamage to internal and associated parts in case the machine is dropped.The disclosed machine is adapted to operation by air under pressure, andis suited to either wet or dry rubbing operations. The body serves as ablock or stationary part of an air operated motor includingreciprocatingI parts to which rubbing shoes 25 and 26 are attached; therubbing shoes 25 and 26 being normally in spaced relationship to oneanother and preferably driven in opposed cycles of reciprocatingmovements. A liquid jet 21 is secured to one side of the body andextends between theA rubbing shoes for applying liquid to the surface ofthe workpiece during wetrubbing operations.

The rubbing shoes 25 and 26 are alike in their structure, so that adescription of one will suice for both. Each embodies a shoe plate 28 ofgenerally rectangular shape and has a substantially plane bottom surface29 to which a pad 30 of' a relatively soft material, such as rubber orfelt, is secured for most rubbing operations. Sheet material 32, such assand paper, is removably applied to the rubbing shoes, so that it coversthe exposedk face of the pad and extends upwardly over the exposedopposite ends of4 theV rubbing shoes, as shown in Fig. 1. Atthoseexposed opposite ends of each of the rubbing shoes, manuallyreleasable clips 33 are utilized to secure the sheet material to therubbing shoes.

As depicted in Figs. l to 4 inclusive, my preferred clip structureincludes a block 34 and is secured to or integrally formed upon the topsurface of the rubbing shoe plate. 'I'his block presents an end grippingsurface 35 facing toward the adjacent end of the shoe plate and ispreferably disposed in acute angular relationship to the top surface ofthe shoe plate. Also, the block is preferably disposed at a positionsuch that the gripping surface 35 thereofis displaced inwardly from theadjacent end surface of the shoe plate. At a position spaced from thegripping surface 35, the block has a bearing bore 36 therein, the axisof which is substantially parallel to the gripping surface 35. A link 31of elongated and generally rectangular shape has one side supported forVlimited rotational movement in the bearing bore 36 of the block. Theopposite side of the link is movably engaged by loops 38 and 39'Whichare integrally formed at opposite ends of a substantially C-shaped clipelement 40, which clip element is preferably made of formed sheet metalpossessing some resilience.

A tab 42 is integrally formed on the clip element and projects upwardlyfrom a position between the loops 38 and 39 to provide a handle foractuating the clip between the closed and open positions depicted inFigs. 2 and 3 respectively. The block, link and clip element are sodisposed and proportioned that a gripping edge 43 of the clip elementfirmly and tightly engages a marginal portion of the sheet material whenthe link is swung to a position away from the gripping surface 35 oftheblock and adjacent the top face ofthe shoe plate 28, whereby thesheet material is grippedebetween the gripping edge 43 and grippingsurface35, as shown in Fig; 2. By swinging 4 the link upwardly with theaid of the tab 42, as shown in Fig. 3, the sheet material is quicklyreleased. It may be noted that as the clip element moves toward itsgripping position, it tends to draw the sheet material tautly across theface of the rubbing shoe pad 3U.

Referring more particularly to Figs. 5 to 10 inclusive, of the drawings,the body 2U of my portable rubbing machine is a block-like cast metalstructure which is designed not only for neat and streamlined appearanceand convenience in use, but also with a view to minimizing weight andmaterially lessening necessary machining operations such as drilling. Amain block 44 has a longitudinal bore 45 extending therethrough from aplane end surface 46 to an opposed plane end surface41. At the ends ofthe longitudinal bore` 45, cylinder liners 48 and 49, in the form ofcylindrical shells, are pressed into the bore to define coaxialcylinders 50 and 52. Internal cavities 53 and 54 in the main block 44.encompass top and side portions of the cylinder liners 48 and' 49respectively to limit the weight of the body, aswell as to affordlongitudinal balance; the cavity' 53 being larger than the cavity 54,whichV latter cavity is adjacent the recess 24 at one end of the block.

At the mid-portions of each of the cylinder lin-- ers 48 and 49, and atwhatl is normally the bottomside of the machine, longitudinallyelongated slots 55 and 56 extend through the cylindery liners.

Aligned with those slots, and alsov aligned longitudinally of the body,slots 51v and 58- extend through a bottom wall 59v of the main block. Asdepicted in Fig. 9, a passage 60 in the ymain blocky valve cavity havinga substantially cylindrical' lower portion 63 and a threaded upperportionY 64. Coaxially with the valve cavity, a bearing bore 65 extendsthrough the body in a direction lateral to the axis of the longitudinalbore 45. A sleeve bearing 66 is mounted in the former bore and extendsacross the mid-portion ofthev longitudinal bore between the cylinderlinersv48 and 49.

In order to minimize drilling operations inthe main block andparticularly in the instanceV of' longer passages and those havingangularly1dls posed portions which would complicate the drilling of suchpassages, the disclosed structurer includes metal tubes which arepositioned in the mold for the block, so that those tubes are cast' Asdepicted. in:

into the block when it is made. Figs. 6, '1 and 8, a tube 61 is castinto the main block to provide an air flow passage extendingfrom oneside of the plane end surface 41 to-the cylindrical lower portion 63.ofthe valve cavity. Another tube 6B extends from the plane end surface 41of the block to the mid-portion of one sideof the block near the bottomthereof toprovide a. passage for the ow of liquidutilized infwet rub-Abing operations. As shown'in Figs. 7,18 and 9, a third tube G9 extendsfrom one end surface of the main block to the other in substantiallyIparallel relationship to the main bore 45. A drilled passage 10 providescommunication for the ow of air from the lower surface of the valvecavity to the tube 69. Another drilled passage 1-2 extends from thelower surface of the valvecavityY to main bore 45 at the mid-portion ofthat main bore. Still another drilled passage 13 which commumcates withthe` valve cavity, asshown in Fig.

5, adjoins an angularly disposed passage 14 'to provide communicationbetween the valve cavity and the internal cavity 53 in the main block.

Pistons 15 and 16 are mounted for reciprocating movement and in opposedrelationship in the cylinder bores 50 and 52 provided by the cylinderliners 48 and 49 at the opposite ends of the longitudinal bore 45.Piston rings 11 and 18 at opposite ends of each o the pistons, andmounted in ring grooves, serve to prevent leakage of air under pressurearound the respective pistons. In order to minimize the vibrationeffected by rapid reciprooation of the pistons within the cylinderbores, as well as to improve mechanical efficiency and limit the overallweight of the machine, I prefer to use pistons of like structure havinghollow end portions 19 and 80 which are closed at opposite ends of thepistons by metal disks 82 and 83 pressed into annular recesses B4 and 85at the opposite ends of the respective pistons. The lengths and strokesof the pistons are s related to the lengths of the slots 55 and 56 inthe cylinder liners that the pistons cover those slots at all points oftheir respective travel strokes. Midway between their respective ends,partitions 86, of substantial thickness, extend laterally across thepistons between their hollow end portions. These partitions have lateralbores 81 therethrough which are adapted to receive end portions ofdriving posts 88 and 89 with a running t; those driving posts preferablybeing secured in place with respect to the pistons by pins 90 and 92extending through the posts and longitudinally of the piston partitions.The driving posts 83 and 89 extend outwardly of the main block throughthe slots 55 and 56 in the cylinder liners and through the aligned slots51 and 58 in the block. At their exposed ends, the driving posts, in thedisclosed structure, have slide receiving shank portions 93 and 94, aswell as shoe supporting feet 95 and 95 integrally formed thereon.

Although the opposed cylinder bores for the respective pistons could becompletely segregated from one another1 by a partition with separate airopenings and valve ports to provide for the flow of air to and from thespaces at the ends of the two pistons, the valve structure is simpliedand the number of required passages and ports minimized by eliminatingsuch partition as in the disclosed structure, so that the air foroperation is fed between and exhausted from the space between theopposed ends of the two pistons. It being my preference that the pistonsshall move vthrough opposed cycles during operation, it may be readilyunderstood that the introduction of 4air under pressure between thcopposed ends of the pistons effects their outward movements in oppositedirections. At the opposite ends of the main block, the cylinder boresare closed by end caps S1 and 98. As shown in Fig. 7, the end caps 91and 98 have channels 99 and |00 in their inner faces for providingcommunication between .the opposite ends of the tube 69 and the outerends of the cylinder bores, whereby air under pressure fed through thetube 69 effects opposed and inward movement of the pistons, whileoutward movement of the pistons exhausts the air through that same tube.

As shown in Figs. 5 and 6, the end cap 98 of the disclosed structure hasadjacent and substantially parallel valve ports |02 and |03 extendinginwardly from a top recess |04 which forms a continuation of the recess24 in the block.

The bottom of each recess communicates with a lateral bore,` such as I05, extending to the' outside of the end cap and adapted to receive athreaded fitting such as |06 on a hose line or the like. Valve seats |01and |08 are mounted within the ports |02 and |03 and are held in placetherein by screw plugs |09 and ||0. Movable valve elements ||2 and ||3are carried by the valve seats |01 and |08 and are biased by springs ||4and |I5 to position such that they normally close passages IIB and ||1in the valve seats. The valve seat |01 has a passage ||8 therein whichcommunicates with the end 0f the tube 61, so that the valve is adaptedto control the ilow of air therethrough to the valve cavity 62.Likewise, the valve seat |08 has a passage ||9 therein whichcommunicates with one end of the tube 68 to control the ow of liquidthrough that tube during wet rubbing operations. Stems |20 and |22extend from the movable Valve elements |2 and I3 through the screw plugs|09 and |'|0 and plroject into the recess |04 in adjacent relations 1p.

Although separate actuating members might be provided for eiectingmanual control of the movable valve elements ||2 and ||3, I prefer toactuate both valves by the single actuator 23, so that the flow ofliquid for wet rubbing operating is controlled simultaneously with thecontrol of the air which effects operation of the rubing machine. Theactuator 23, in the disclosed structure, comprises a shell having anexposed wall |23 which conforms to the general contour of the body, andside walls |24 which extend into the aligned recesses 24 and |04 in theblock and end cap. A leaf |25 secured to the lower surfaces of the sidewalls |24 of the actuator hasacurved portion |26 at one end whichengages a cross pin |21 at the inner end of the recess, so as to supportthe actuator for limited rocking movement within the recess. At the endof the leaf opposite the pin |21, that leaf engages the projecting endsof the stems |20 and |22. Intermediate the ends of the actuator, alignedslots |28 are provided in the side walls, which slots engage inwardlyprojecting studs |29 on opposite sides of the recess to guide theactuator and limit the outward movement thereof.v It may be observedthat the valve springs ||4 and ||5, in addition to biasing the movablevalve elements to their closed positions, normally bias the actuator toa position projecting outwardly somewhat from the walls of the body.Thus, inward movement of the actuator by the manual operation Aofpressure thereto opens both the air and liquid valves.

Externally of the body, the bottom wall 59 preferably presents asubstantially plane surface |30. As illustrated in Figs. 5, 9, 10 andl2, that bottom wall 59 of the body is provided with grooves |32 and |33which are equally spaced on opposite sides of the slots 51 and 58 andextend longitudinally of the body in substantially parallel relationshipto the axis of the longitudinal bore 45. In the present instance, thesegrooves are arcuate in shape and are of a depth substantially less thana semi-circle. They carry slide bars |34 and |35 of circular sectionwhich are secured in place by end cross clamping strips |36 and |31 heldin place by fastening means, such as screws |38. As shown in Figs. 5, 9,10, 11 and l2, a slide |39 has parallel and arcuate grooves |42 and |43therein which are adapted to fit for sliding movement at one end of theslide bars |34 and |35. Likewise, a slide |40 has parallel and arcuategrooves |44 and |45 therein which are adapted to` fit for slidingmovement at the other ends of: the slide bars |34VV and |35. In theassembly; as depicted in Figs. and 9, openings |46 and |.41 in theslides fit onto the shank portions 93' and 94.V of the drive posts 88and 891 and are secured inplace against the feet 95v and 96 on those.postsxby fasteningy means, such as screws. |48.

Substantially.: parallel. arms |49V and |5|l-` pro.- jectfromadjacentends of the slides |39 and |.40,.respectively. and are normally disposedwith their., end: portions in. adjacent andl side-by-side relationship.At their adjacentendsand inopposed relationship, thev arms: |49. and`|50 have lateral channels |52'and |53 therein, which'chan.- nels carryslide; blocks |518l and |55 for sliding movement in a= direction lateralto the sliding movementsofftheslides |,39 and |49. An oscillator shaft|56 is journalled in the sleeve bearing 66. AtV one end, thisoscillatorshaft has a cross head |51 drivingly secured thereto, While the otherend thereof extends into the valve cavity 6.2; At its opposite ends,the. cross head |51 has studs |58 and |59 projecting therefrom andextending into bearing bores |66 and |62 in the slide blocks |54 and |55respectively. As depicted in Figs. and 12, the slide bars |313 and |35have arcuate notches |63 and. |64 at their mid-portions,l that theyclear the opposite ends' of" thecross head- |51. posts 88 and 89u aredirectly secured to the pistons -.and 16, reciprocating movement ofthose pistons. producessimilar reciprocating movements oftheslidesv |39and |49. The arms |46 and |58 move with the-slide and in opposeddirections to effect: oscillatory rotational movements'of the crosshead|51 and oscillator shaft |56; it being understoodA that the slide blocks|54 and |55 provide compensation between the linear movements of thearmsl |49. and |58 and the ary cuate movements of the studs I 60v and|62 which are carried by cross head |51.

In addition to servingas guides for the movements of the rubbing shoes,the slides E39 and |48 act through the arms |49 and |50 to effectoscillating rotational movements of the oscillator shaft |56, thefunction of which shaft is to drive an. operating valve |65:which isdisposed in the valvel cavity 62 for controlling the flow of air to andfrom the cylinder bores at opposite ends of the pistons in timedrelationship to the piston movements. As shown in Figs. 1l, 13and 14,the'valve cavity 62 has a planeY bottom surface |614 throughv which thepassages-10, 12 and 13 pass in' spaced relationship to one another. Inthe disclosed structure, the passages 10, 12 and 13 are concentricallydisposed and are spaced at positions substantially 90 apart with respectto the axis of the oscillator shaft |56. In spaced relationship withrespect to those openings, a pin |68 is mounted in an opening in themain block and projects into. the valve recess at a position spaced fromthe oscillator shaft.

In order to prevent wear on a portion of the block itself and so as toprovide a replaceable and hardened wearing element, astationary valveplate |69 is mounted in the valve cavity against the plane bottomsurface |61; that stationary valve plate having an opening |10 thereinwhich fits snugly upon the pin |68 to hold it stationary. In alignmentwith the passages 19 and 12, the stationary valve plate has ports |12and |13 extending axially therethrough, which ports preferably havestraightl side edges to improve their closing and opening actions. Atthe center, the stationary valve plate has an opening |14 through Sincethe driving l...

8. which the oscillator shaft |56 extends. Between the ports |12 and |13and in communica'.- tion with the passage 13, the stationary plate hasan arcuate slot |15v therein.

A valve rotor |16 has a central opening |11 therein through which theoscillator shaft |56 extends for free rotational movement relativethereto. This valve rotor embodies an arcuate, channel |18 in its lowersurface which is adapted to provide communication between the arcuateslot |15 and one or the other of the ports |12 or |13 in the stationaryvalve plate |69. The channel |18 does not extend through the movablevalve rotor, because its primary purpose is to provide communication tothe exhaust passage 13 through which air is released from one end ofeach of the pistons, while air under pressure isV fed to the other endthereof. On the other hand, notches |19 and |88 are provided at spacedpositions separated from the ends of the channel |18 to control the flowof air to one or theV other of the ports 12 or |13. In respect to theuse of the channel for controlling the now of air to the exhaustpassage, as contrasted with the use of notches in the movable Valveplate for controlling the flow of air to the inlet ports, it is to berecalled that the valve cavity, during operation7 contains air underpressure which isk fed thereto through the tube 61. The two extremepositions of the movable valve plate are illustrated in Figs. 13 and 14.In Fig. 13, air under pressure from the passage provided by the tube 61is being supplied to the outer ends of the cylinders through the passage1D, while air is being exhausted from betweenA the pistons through thepassage 'i2 and the passage 13. In the position shown in Fig. 14, theexhaust is from the ends of the cylinders, While the input of air underpressure is directed to the space between the pistons.

In connection with the exhausted air, it may be observedl that such airowing outwardly through the passage 13 in the valve cavity and passage14, as depicted in Figs. 5 and 9, flows into the cavity 53 in the body.From that cavity, as shown in Fig. 9, it flows through the passage 60into the slot 51, from which it escapes from the lower portion of themachine around the slides and adjacentthe shoes. Thus, the. body servesas a muffler for quieting the operation of the machine.

As has been explained, the oscillator shaft |56 is driven in timedrelationship to the movements of the pistons. As shown in Figs. 5 and11, the oscillator shaft has a notched end- |82 presenting-a flatdriving surface within the valve cavity. This notched end fits into acorrespondingly shaped opening |83 in a valve actuating cam |64. In theassembly of the valve, the movable valve plate |16 rests upon thestationary valve plate |59 and the valve camis disposed against themovable valve plate |16 while en gaging the notched end |82 of theoscillator shaft. Also, the movable valve plate 16 has a stud |85projecting upwardly from the top surface thereof between the notches 19and |80, which stud is disposed in a slot |86 in the cam |84. With thiscombination of structure, the movable valve part is driven in timedrelationship to the piston movements and thereby effects an efficientand effective alternation of the iiow of pressure and exhaust air to andfrom the cylinders at opposite ends of the pistons, so as to producereciprocating movements of the pistons in opposed cycles. In order tohold the valve parts inV their assembled relationship, as

shown in Fig. 5, as Well as for sealing the valve cavity, a valve cap|8| is threaded into the upper portion 64 of the valve cavity. Acompression spring 19| is disposed between the valve cap |8| and the cam|84 in a recess 29| in that valve cap, whereby to urge the valve partsinto rm engagement. The valve structure is readily disassembled byremoval of the cap Iii, so that the spring and valve parts are readilyaccessible.

As shown in Figs. 5, 9 and 10, it is my preference to provide an apron|87 having side flanges |88 which t over lower marginal portions of themachine body, as well as a face portion |89 which covers the slides andhas openings |90 and |92 therein for passage of the feet 95 and 96therethrough. Pads |93, |94 and |95 of felt or the like are interposedbetween the face portion of the apron and the lower faces of the slidesand arms. These pads, in addition to controlling the outward ow ofexhaust air during operation of the machine, serve to prevent dust anddirt from getting into the operating parts of the machine.

In addition to the previously described shoe plates 28 and pads 30, eachof the shoes 25 and 26 has a top plate |98 secured thereto by fasteningmeans, such as rivets |91, as shown in Fig. 5. A shoe supporting stud|98 having a head portion |99 is held in place and extends upwardly fromeach of the shoes to serve as a mounting element for securing the shoesto the feet 95 and 96. A notch 200 is provided in one side of each ofthe studs. Also, the feet 95 and 96 have axial openings 202 thereinwhich snugly nt the projecting studs. For securing the rubbing shoes inplace, a set screw 203 is threaded into an outside end of each of theslides and has a tapered end adapted to engage the notch 200 in the studto draw that stud inwardly as the screw is tightened. Aligned openings204 and 205 in the apron and clamping straps provide access to the endsof the set screws for effecting the removal and installation of theshoes relative to the machine.

While I have illustrated a preferred embodiment of my invention, manymodications may be made without departing from the spirit of theinvention, and I do not wish to be limited to the precise details ofconstruction set forth, but desire to avail myself of all changes withinthe scope of the appended claim.

Having thus described by invention, what l claim as new and desire tosecure by Letters Patent of the United States, is:

A portable rubbing machine adapted to operation by air under pressureand comprising, in combination, a cast body exteriorly contoured toprovide a hand grip and having a longitudinal bore extendingtherethrough, a cylinder liner defining a cylinder and mounted in eachend of the longitudinal bore, said body having cavities thereinpartially encompassing the mid-portions of the cylinder liners, saidbody and the cylinder liners also having aligned slots therein openingoutwardly opposite the cavities and a passage providing communicationfrom one of the cavities to one of the slots, double acting pistonsmounted for reciprocating movement in the cylinders and covering theslots in all positions of the pistons, end caps secured to opposite endsof the body for closing the opposite ends of the cylinders, one of saidend caps having an air ow passage therethrough and a valve therein forcontrolling the flow of air through the passage, said body having avalve cavity therein near the mid-portion of the longitudinal bore andnormally closed by a removable cap to form a valve chamber, said bodyhaving passages therein for the flow of air from the air passage in saidone of the end caps to the valve chamber and from the valve chamber toopposite ends of the cylinders, additional passages in the body for theflow of air from the valve chamber to the longitudinal bore at aposition between the pistons and from the valve chamber to one of thecavities, a valve in said chamber for effecting air now in alternatingsequence to the cylinders at opposite ends of the bore end and to thelongitudinal bore between the pistons, the last mentioned valve alsocontrolling the exhaust of air alternately from opposite ends of thecylinders to said one of the cavities, a slide and a rubbing shoe havingsubstantially a direct and straight line connection to each of thepistons for actuation thereby, and means actuated by the slides formoving the last mentioned valve in timed relationship to the movementsof the pistons, said last mentioned valve including a stationary platehaving a single exhaust port and two inlet ports therein, a valve rotorengaging the stationary plate and having notches and a passage thereinproportioned and disposed with respect to the exhaust and inlet ports inthe stationary plate so as alternately to connect one of the inlet portsto the exhaust port while alternately exposing the other inlet ports toair under pressure in the valve chamber, a valve cam for actuating thevalve rotor, and a shaft connected to the slides for eiectingoscillatory movement of the cam.

HAROLD R. JOHNSON.

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